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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI: same ISIDEddy, The purpose here is not what you are looking at. First, the Target iSCSI (SCSI) Port can inspect all the session arriving at its Portal Group, to see if any have the same Initiator name and ISID as another one. If so, it is Not Logged-in. This would be parallel Sessions from the same initiator. Second, when an Initiator comes back after a failure, they should use the same ISID they had previously, thereby permitting approprate Nexus to be continued e.g. Persistent Reserves, etc. The second point was the primary reasons for the Conservative reuse. Before this statement, some folks were using a different ISID for each Target Node with which they were working. Then the ISID space could get used up, and then as sessions were stopped and restarted, they would retrieve an ISID from an available pool of ISIDs, and as a result, the approprate Nexus could not be re-established. Hence the words Conservative Reuse means you keep reusing the same ISID number as often as possible. Therefore, you will probably see an individual Initiator have only 1 ISID, ever used. It is only when a Wedge Driver of some type permits Multiple Initiators from the same Host, that you are likely to see the same Initiator Name, and Different ISID. But Still, into any one portal group and Target iSCSI (SCSI) Port there will only be one active "Initiator Name + ISID" entity. Each unique "Initiator Name + ISID" are treated (today) as if they are as different as if they came from different hosts. . . . John L. Hufferd Senior Technical Staff Member (STSM) IBM/SSG San Jose Ca Main Office (408) 256-0403, Tie: 276-0403, eFax: (408) 904-4688 Home Office (408) 997-6136, Cell: (408) 499-9702 Internet address: hufferd@us.ibm.com "Eddy Quicksall" <Eddy_Quicksall@ivivity.com>@ece.cmu.edu on 12/20/2001 10:39:27 AM Sent by: owner-ips@ece.cmu.edu To: "ips@ece. cmu. edu \(E-mail\)" <ips@ece.cmu.edu> cc: Subject: iSCSI: same ISID Section 9.1.1 says: the same ISID should be used in the Login process to multiple target portal groups (of the same iSCSI Target or different iSCSI Targets). Note that the ISID RULE (2.5.3) only prohibits reuse to the same target portal group. It also does not "preclude" reuse to other target portal groups. The principle of conservative reuse "encourages" reuse to other target portal groups. When a SCSI target device sees the same (InitiatorName, ISID) pair in different sessions to different target portal groups, it can identify the underlying SCSI Initiator Port on each session as the same SCSI port (in effect, it can recognize multiple paths from the same source). This is good but the target will still have to sort out ISID's when they are different under the same situations named above. So, since the target still has to have all the code to sort this out, what good is this statement? I think the only thing keeping us from saying you MUST use the same ISID's is the fact that we have allowed an iSCSI Initiator to have more than one session to the iSCSI Target Portal Group. Is that really necessary? If not, then we could make this a MUST and simplify the target code. Eddy
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